Gyro Over-mold vs Single-mold
About 2 weeks ago, there was a post on the disc golf Reddit questioning the legitimacy of the Gyro over-mold tech that MVP uses on their discs versus a conventional single-mold disc. While I personally bag a pure MVP bag, and for me the claims felt valid so I never dug deeper. But for the sake of science, and to see if my gut instinct about MVP was true, I decided to order a couple of discs in the same weight, category, and rough dimensions. Also MVP is all about science, so I figured it would be a good experiment, for science!
Now, originally I ordered the Photon and Destroyer, but forgot that the Photon is an 11 speed rim, and the Destroyer is a 12 speed rim. Due to size difference, not a good comparison, even if doable. I then ordered the Wraith and the Defy. Those complimented better, but measurements wise, the Photon and the Wraith matched up better. I provide all my measurements in the table below for your own perusal. All measurements were done with calipers.
| Disc | Rim Width | Rim Height | Diameter | Inner Diameter | RW to Di Ratio | IDi to Di Ration | RH to RW Ratio |
|---|---|---|---|---|---|---|---|
| Wraith | 21.5mm | 12.1mm | 20.95cm | 16.68cm | 10.47% | 79.6% | 56.27% |
| Defy | 21.3mm | 10.8mm | 21.01cm | 16.69cm | 10.13% | 79.40% | 50.7% |
| Photon | 21.8mm | 10.94mm | 21.08cm | 16.68cm | 10.34% | 79.13% | 50.18% |
| Destroyer | 22.8mm | 11.8mm | 21.03cm | 16.4cm | 10.84% | 77.97% | 51.75% |
RW = Rim Width, RH = Rim Height, Di = Diameter, IDi = Inner Diameter
Based on the numbers, the Photon and Wraith were the closest for comparison. So I chose those to do the cutting with.
So after cutting the stuff out and weighing it, here are the results.
| Disc | Rim | Plate | Rim % | Plate % |
|---|---|---|---|---|
| Wraith | 130g | 45g | 74.29% | 25.71% |
| Photon | 136g | 39g | 77.71% | 22.29% |
So far, it seems there is a 3.5% more weight in the Photon rim compared to the Wraith rim. While doing this, I measure 137g/38g for the photon rim, so it might be just on the edge there. which is about a 4% rim difference.
So the main claim that there is more weight in the rim on an MVP disc is true. But I also noticed that the plates were roughly the same surface area, but had substantially different weights. the Proton rim was a whole 13.4-15.6% lighter (depending on if its 39g or 38g). So that means that the proton plastic is lighter for the same space that the rim takes up. Since its part over-mold, and part proton plastic.
So I cut the cross-section.
So, from here I did some additional measurements, that I have in the table below.
| Disc | Rim Height Full | Plate Thickness | Mid-Rim Height | Triangle Base | Triangle Height |
|---|---|---|---|---|---|
| Wraith | 13.40mm | 1.65mm | N/A | N/A | N/A |
| Photon | 13.25mm | 1.44mm | 7.3mm | 2.57mm | 3.19mm |
So, firstly, I didn’t do some of the measurements for the Wraith, as for one, the Wraith’s rim is equally distributed through the entire rim, and is not 2 pieces.
We will breakdown the total amount of rim plastic that is Proton into smaller pieces. First the trapezoid that makes up the main portion. We find the area of a trapezoid, which is (A = height * {(base1 + base2) \over 2} ). So, base1 = 7.3mm, base2 = 13.25mm, and height is 10.65mm (forgot to measure this for the table).
This gives us an area of 109.42mm squared.
The little triangle is a (A = {1 \over 2} base * height), which gives us an area of 4.10 mm squared. combine the two and we have a total area of 113.52mm squared.
Now we do something similar for the over-mold, but subtract the 4.10mm of the small triangle, from the area of the bigger triangle, which has a length of is 11.57mm. SO same triangle formula with the triangle base above and the length as the height, gives us 42.01mm squared for a total area of the over-mold to 37.91mm squared.
This lead me to final measurement of 151.43mm squared for the entire rim. Now if you are a skeptic individual and double checking math, and you treated the entire rim as a triangle and used the rim width of 21.8 and the height of 13.25mm above, you will find the area is 144.42 mm squared. but that could be attributed to growing user error, and the non-exactness of measuring this all manually.
So at 151.43mm as our total rim area. it makes the proton plastic portion take up 74.9% of the space in the rim. In a normal disc, 74.9% of the rim would weight 74.9% of the total weight. In the Wraith’s case, that is 97.37g. But in this over-mold, since the plastic is 14.5% lighter (average of the 2 ends of the range above). that means for the same space, the rim of the Photon is 14.5% lighter. So if we take 74.9% of the 136g is 101.86g. We take an additional 14.5%, that gives us 87.09g.
Meaning the over-mold is 48.91g, while the same area on the Wraith would be 32.63g. MVP has 33.28% more weight on that half of the rim of the Photon compared to the Wraith.
So in conclusion to all this. MVP’s discs not only have more weight in the rim in general, that weight is shifted more to the over-mold on the disc edge. Making MVP’s gyro tech claims pretty legit in my opinion.
Other Observation:
- Proton was much harder to poke through and cut. It took me about 2x longer to get the plate out due to how hard it was to cut through the plastic.
- The over-mold plastic is a bit less durable than the Proton though. It was about as easy to cut as the Champion plastic in comparison.
- 15 grams doesn’t sound like a lot, but when the difference of a 160g disc and 175g disc affects flights, 15 grams in the rim could make a difference too.
Final Disclaimer: This is all pretty rough math. I don’t have the tools or time to go deeper, I already spent 3 hours on just this. If you want more exact numbers, or to disprove mine, feel free. But I think this is sufficient enough for me.
[Update 1/23/2019]: I will be doing a Part 2 with Fission, Blizzard, and Starlite plastic to test this on special lightweight discs.
[Update 3/05/2019]: Part 2 is complete and can be read here.
